Initial Hash of Hash by value

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I am attempting to initialize the values of keys of hashes from a single hash. Instead of all the hashes being initialized by value, the values are all references to the same hash, which I don't want. What is the best way to set up all the hashes with the same structure/values of the one hash without just passing reference? In the example below, I would like the values of hash3 and hash4 to be the key/value pairs of hash1 and hash2. However, what I am getting is the values are being set to references, which means I cannot change the values of hash3 and hash4 independently.

use warnings;

my %hash1 = (
    bush => "A",
    tree => "A"
);

my %hash2 = (
    dog => "A",
    cat => "A"
);

my %hash3 = (
    plants    => \%hash1,
    animals   => \%hash2
);

my %hash4 = (
    plants    => \%hash1,
    animals   => \%hash2
);

print "$hash3{plants}{bush}\n";
print "$hash4{plants}{bush}\n";
print "\n";
$hash4{plants}{bush}="B";
print "$hash3{plants}{bush}\n";
print "$hash4{plants}{bush}\n";
[download]

Comment on Initial Hash of Hash by value Download Code

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Re: Initial Hash of Hash by value by wind (Priest) on Apr 07, 2011 at 18:25 UTC
Create new anonymous hashes if you want the structures to be independent: `my %hash3 = ( plants => {%hash1}, animals => {%hash2}, ); my %hash4 = ( plants => {%hash1}, animals => {%hash2}, );` [download]	[reply] [d/l]
Re: Initial Hash of Hash by value by FunkyMonk (Bishop) on Apr 07, 2011 at 18:30 UTC
You can easily create new references to your original hashes like so: `my %hash3 = ( plants => { %hash1 }, animals => { %hash2 } ); my %hash4 = ( plants => { %hash1 }, animals => { %hash2 } );` [download]	[reply] [d/l]
Re: Initial Hash of Hash by value by believer (Sexton) on Apr 11, 2011 at 13:06 UTC
If you want to copy nested hashes, consider Storable dclone. For example, if %hash2 looks like this: `%hash2 = ( mammal => { dog => 'a', cat => 'a' }, bird => {...}, ... )` [download] { %hash2 } will only copy the data 1 level deep. edit: removed link to perl cookbook	[reply] [d/l]